What to do against ageism? You might try one of the following strategies to prevent age becoming an issue at your interviews:
Focus on your energy, not your experience
If you speak about your enthusiasm, you won't need to discuss how many years experience you have. Focus on how you are looking forward to this new opportunity. Don’t emphasise your long years of experience (although that, of course, is perfectly valid) because there may be the unintended consequence of putting the focus on your age.
Be more of a consultant
If you approach the interview with the mindset of a consultant, you will lead conversations in which you can show your curiosity and willingness to learn. Ask open-ended questions and be an engaged listener. This will help you understand the context and also spot challenges. You can then identify where you can add most value. 
You will thus make the impression of someone who is confident. You will also seem less desperate to get the job, according to the Harvard Business Review.
Demonstrate humility
If you show genuine humility, making it clear you don’t mind working with others and don’t insist on hierarchy, there is a good chance ageism will not harm your chances. Talk about teams, what current employees have achieved, and how you could foster collaboration.
Connect with your interviewer
Start by displaying warmth because that is how you can influence others: a mere smile is enough. Try to find ways to connect personally with your interviewer. You might make references to popular shows or use humour. But don’t use self-deprecating humour such as "that was before the internet": this might make people feel uncomfortable. 
-jk-
 
 